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Watching African Wave 91L; Rare September European Heat Wave Smashes Records

By: Jeff Masters 3:45 PM GMT on September 04, 2015

A strong tropical wave with plenty of spin and heavy thunderstorm activity (Invest 91L) moved off the coast of Africa on Thursday, and is headed west at 15 - 20 mph, on a path that will take it a few hundred miles south of the Cape Verde islands over the weekend. The 00Z Friday (8 pm EDT Thursday) runs of one of our top three models for predicting tropical cyclone genesis, the GFS model, showed development of 91L into a tropical depression by Tuesday midway between Africa and the Lesser Antilles Islands. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development of 40% and 60%, respectively. The tropical Atlantic is relatively moist, has the highest sea surface temperatures of the year, and is expected to have low to moderate wind shear, conditions which favor development. The wave should take about 6 - 8 days to make it to the Lesser Antilles Islands.

Figure 1. MODIS image of Invest 91L off the coast of Africa taken at approximately 8:15 am EDT Friday, September 4, 2015. Image credit: NASA.

Fred barely alive
Tropical Depression Fred continues to barely hang on as a tropical cyclone in the waters of the Eastern Atlantic, but high wind shear is expected to kill Fred by Saturday. However, Fred could spring back to life in 3 - 5 days, when the storm will encounter lower wind shear and anomalously warm waters of 27.5°C (82°F), over 500 miles southwest of the Azores Islands. Fred could affect the Azores 6 - 7 days from now, but it is too early to judge the risks of this.

The remains of Tropical Storm Erika are still generating some disorganized shower activity off the Southeast U.S. coast, but high wind shear will prevent re-development.

Figure 2. From left to right: Typhoon Kilo, Hurricane Ignacio, and Hurricane Jimena spin across the Pacific Ocean as seen by Aqua/MODIS at 02:40 UTC September 3, 2015. Image credit: NASA.

A Busy Pacific for Tropical Cyclones
Four tropical cyclones continue to spin over the North Pacific, though none are expected to threaten land over the next five days. Tropical Storm Kevin in the Eastern Pacific, with top sustained winds of 60 mph at 11 am EDT Friday, is feeding moisture in the Southwest U.S. monsoon, and will contribute to isolated heavy rains over Arizona and New Mexico over the next few days. No flood watches or warnings were up on Friday for the anticipated rain, though. Kevin is expected to turn west and head out to sea, eventually succumbing to high wind shear and mid-level dry air. In the Central Pacific, Hurricane Jimena is slowly weakening, with top sustained winds of 85 mph at 11 EDT Friday. Recent runs of the GFS and European models continue to predict that Jimena will approach Hawaii from the northeast late next week as a tropical storm, and pass within 200 miles of the islands. Meanwhile, Hurricane Ignacio, now a Category 1 storm north of Hawaii, is weakening as it heads north towards the Gulf of Alaska. Ignacio is expected to transition to a powerful extratropical storm by Monday, and bring heavy rains to Britich Columbia on Tuesday. Long-lived Typhoon Kilo is now in its 15th day as a tropical cyclone, including a long spell as a major hurricane. Kilo is predicted to steadily re-intensify over the weekend, reaching Category 4 strength by Sunday as it moves on a westward path that will likely take it several hundred miles north of Wake Island. Kilo is likely to be around until at least September 11, and may pose a threat to Japan 6 - 7 days from now.

One "sleeper" system to watch is an area of disturbed weather in the Northeast Pacific located several hundred miles south-southwest of Manzanillo, Mexico. Slow development of this system is possible during the next several days as the low moves northwestward and gradually merges with another disturbance to its west. The models are not handling this merger well, and this system may end up being of concern to Mexico's Baja Peninsula. In their 8 am EDT Friday Tropical Weather Outlook, NHC gave 2-day and 5-day odds of development of 10% and 40%, respectively.

Rare September Heat Wave Scorches Europe
Meteorological summer is over in Europe, but a rare and extraordinarily intense heat wave has kept its grip on much of the continent during early September. Hundreds of European cities broke all-time September heat records the past three days; some stations with long periods of record exceeding a century saw their records smashed by 7 - 8°F--"a margin rarely seen before in the world," in the words of weather records researcher Maximiliano Herrera, who has been tabulating the new records.

Figure 3. Historians recover relics from the 17th century on the bed of the Vistula River in Warsaw, Poland on September 3, 2015. The water level of the Vistula, Poland's largest river, is at its lowest level since measurements began in 1789, due to severe drought conditions. The treasures being excavated were looted by an invading Swedish army in the mid-17th century and got buried in the Vistula when a Swedish barge sank. Jewish tombstones and wreckage from a WWII fighter plane have also been uncovered this summer from the Vistula and its tributaries due to the low water levels. Image credit: JANEK SKARZYNSKI/AFP/Getty Images.

September 1, 2015: a rare day in the annuals of climatology
The carnage began on September 1, with September national heat records falling in eight countries. Notably, the new national heat record set in Lithuania was more than 3°C (5.4°F) higher than the previous September record--an astonishing margin for a monthly national record in a nation with dozens of reliable stations with a period of record extending back nearly 150 years. Here are the eight nations that set new September all-time heat records on September 1, 2015, according to Maximiliano Herrera:

Moldova: Tiraspol, 38.4°C (101.1°F)
Ukraine: Voznesens'k, 38.8°C (101.8°F)
Austria: Pottschach, 36.0°C (96.8°F)
Czech Republic: Javornik, 37.4°C (99.3°F)
Slovakia: Michalovce, 36.4°C (97.5°F)
Poland:  Tarnow, 36.8°C (98.2°F)
Belarus: Zitkovici, 35.6°C (96.1°F)
Lithuania: Druskininkai, 35.1°C (95.2°F)

All-time September heat records were smashed at individual stations in many other countries, including Russia, Romania, Bulgaria, Serbia, Montenegro, Macedonia, Kosovo, Bosnia and Herzegovina, Croatia, Slovenia, Italy, San Marino, Hungary, and Germany, with 48 stations in Germany alone setting new all-time September heat records (thanks go to Dr. Michael Theusner for this stat.) Some stations with more than a century of data even managed to beat their ABSOLUTE records for any month.

Figure 4. Severe drought had much of Europe in its grip by mid-August, 2015. Image credit: European Drought Observatory.

September 2 and beyond: more record heat
The incredible heat continued on September 2, shifting eastwards some, with a 38.6°C (101.5°F) at Falesti, Moldava beating that nation's all-time September heat record set just the previous day. Ukraine tied its national record, just set the previous day. The extreme heat backed off considerably on September 3 and 4, but will build back in again over Southeast Europe over the weekend, with more all-time September heat records likely to fall.

European drought cost this summer: $2.7 billion
It's been a incredible summer for extreme heat in Europe, with Germany setting its all-time heat record (twice), and with hundreds of stations having long periods of record setting all-time heat records. The heat has been responsible for hundreds of heat deaths in Europe, and according to the August 2015 Catastrophe Report from insurance broker Aon Benfield, drought in Romania, Poland, and the Czech Republic this summer has cost at least $2.7 billion--just below the $3 billion price tag of the California drought.

We’ll be back with an update on the tropics on Saturday. Have a great Labor Day weekend!

I'll be on the Weather Underground TV show (#WUTV on Twitter) tonight on The Weather Channel. The show airs between 6:00 and 8:00 pm EDT. If you don’t have access to TWC on cable, you can still access selected clips from each episode, live streaming of online-only content, and a WUTV chatroom, all on the Weather Underground WUTV website.

Jeff Masters

Hurricane heat Drought

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.